In a switching network, a plurality of trunks or links come together in a network node. Switching networks are provided in the network nodes for random connection of the trunks.
For example, IEEE Journal on Selected Areas in Communications, Vol. 9, No. 8, October 1991, discloses a two-stage, modularly constructed switching network in reversal grouping, wherein the switching network is connected to a plurality of duplex trunks each respectively established by a simplex input line and a simplex output line. The switching network is formed by a plurality of switching modules arranged in stages. Every switching module has the same number of simplex inputs as simplex outputs and every simplex input of a switching module is connectable to every simplex output of the same switching module. Every switching module is formed with a plurality of switching elements having twice as many simplex inputs as simplex outputs. The switching elements are arranged in two rows. A switching element of the second row together with two switching elements of the first row whose simplex outputs are connected to the simplex inputs of the switching element of the second row form a switching element group. The simplex inputs of the switching modules of the first stage are connected to the simplex inputs of the switching elements of the first row belonging to the switching module and are available for the connection of input lines. The simplex outputs of a switching module are established by simplex outputs of a switching element belonging to the switching module. For switching short-paths, portions of the simplex inputs and of the simplex outputs of a switching module of the first stage that are of the same size are connected to input or output lines, respectively, that belong to the same trunk, whereas the remaining simplex inputs or simplex outputs are connected to links that deliver signals from switching modules of the second stage or forward signals to switching modules of the second stage. Only output lines or only links are connected to the outputs of one and the same switching element group. This switching network has the capability of switching short-paths in the first stage.